Oil is a nonrenewable natural resource having great importance to the industrialized world. The increased demand for and decreasing supplies of conventional oil has led to the development of alternative sources of crude oil such as oil sands containing bitumen or heavy oil and to a search for new techniques for continued recovery from conventional oil deposits. The development of the Athabasca oil sands in particular has resulted in increased proven world reserves of over 170 billion barrels from the application of surface mining and in-situ technologies. There are also large untapped reserves in the form of stranded oil deposits from known reservoirs. Estimates as high as 300 billion barrels of recoverable light and heavy oil have been made for North America. Recovery of stranded oil requires new recovery techniques that can overcome, for example, the loss of drive pressure required to move the oil to nearby wells where it can be pumped to the surface. These two sources of oil, oil sands and stranded oil, are more than enough to eliminate the current dependence on outside sources of oil and, in addition, require no substantial exploration.
Shaft Sinking
Shaft-sinking or shaft-drilling are well-developed areas of civil and mining construction. Applications in civil construction include for example ventilation shafts for transportation tunnels, access shafts for water drainage and sewage system tunnels and Ranney wells for recovering filtered water from aquifers. Applications in mining include for example ventilation and access shafts for underground mine works. Shafts have been sunk in hard rock and drilled or bored into soft-ground. Soft-ground shafts are commonly concrete lined shafts and are installed by a variety of methods. These methods include drilling and boring techniques often where the shaft is filled with water or drilling mud to counteract local ground pressures. There are casing drilling machines that use high torque reciprocating drives to work steel casing into the formation. There are also shaft sinking techniques for sinking shafts underwater using robotic construction equipment. There are secant pile systems, where several small diameter bores are drilled in a ring configuration, completed with concrete and then the center of the ring excavated to create the shaft. There is the caisson sinking method, which formation materials are removed from below the center of caisson, creating a void and causing the casing to sink under its own weight. Soft-ground shafts can be installed with diameters in the range of about 3 to about 10 meters.
Drilling Technology
Drilling technology for oil and gas wells is well developed. Drilling technologies for soft and hard rock are also well known. Water jet drilling has been implemented in both oil and gas well drilling, geothermal drilling, waste and groundwater control as well as for hard rock drilling. An example of water jet drilling technology is provided in published papers such as “Coiled Tubing Radials Placed by Water Jet Drilling: Field Results, Theory, and Practice” and “Performance of Multiple Horizontal Well Laterals in Low-to-Medium Permeability Reservoirs” which are listed as prior art references herein. Prior art “mining for access” methods are based on excavating tunnels, cross-connects and drilling caverns in competent rock above or below the target hydrocarbon formation. The competent rock provides ground support for the operation and, being relatively impermeable, to some extent protects the work space from fluid and gas seepages from the nearby hydrocarbon deposit. This approach cannot be applied when formation pressures are high; when the hydrocarbon reservoir is artificially pressurized for enhanced recovery operations (“EOR”); when the hydrocarbon formation is heated, for example, by injecting steam; or when the ground adjacent to the hydrocarbon reservoir is fractured, soft, unstable, gassy or saturated with ground fluids.
Drilling technology for oil and gas wells is well developed. Drilling technologies for soft and hard rock are also well known. Water jet drilling has been implemented in both oil and gas well drilling, geothermal drilling, waste and groundwater control as well as for hard rock drilling. An example of waterjet drilling technology is provided in published papers such as “Coiled Tubing Radials Placed by Water Jet Drilling: Field Results, Theory, and Practice” and “Performance of Multiple Horizontal Well Laterals in Low-to-Medium Permeability Reservoirs” which are listed as prior art references herein.
One of the present inventors has developed a hybrid drilling method using a modified pipejacking process in conjunction with a augur cutting tool and a plasticized drilling mud to install horizontal wells from the bottom of a distant shaft into a river bottom formation. This technique was successfully used to develop a Ranney well with a long horizontal collector well.
Vertical, inclined and horizontal wells may be installed from the surface by well-known methods. In many cases surface access is restricted and installing wells from an underground platform such as the bottom of a shaft or a tunnel may be a more practical and cost-effective approach to installing wells. Machine and methodology developments, particularly in the heavy civil underground construction sector, have opened up new possibilities for an underground approach for installing wells. Discussing some of these techniques, the present inventors have filed U.S. provisional patent applications U.S. Ser. No. 60/685,251, filed May 27, 2005 entitled “Method of Collecting Hydrocarbons from Tunnels”, and U.S. Ser. No. 60/753,694, filed Dec. 23, 2005 entitled “Method of Recovering Bitumen” both of which are incorporated herein by this reference.
TBM and Microtunneling Technology
Soft-ground tunnels can be driven through water saturated sands and clays or mixed ground environments using large slurry, Earth Pressure Balance (“EPB”) or mixed shield systems. This new generation of soft-ground tunneling machines can now overcome water-saturated or gassy ground conditions and install tunnel liners to provide ground support and isolation from the ground formation for a variety of underground transportation and infrastructure applications.
Developments in soft-ground tunneling led to the practice of micro-tunneling which is a process that uses a remotely controlled micro-tunnel boring machine combined with a pipe-jacking technique to install underground pipelines and small tunnels. Micro-tunneling has been used to install pipe from twelve inches to twelve feet in diameter and therefore, the definition for micro-tunneling does not necessarily include size. The definition has evolved to describe a tunneling process where the workforce does not routinely work in the tunnel.
Robotic Excavation Technology
Robotic excavators have been used in a variety of difficult situations such as excavating trenches undersea or preforming excavation functions underground in unsafe environments. An example of this technology can be found, for example, in U.S. Pat. No. 5,446,980, entitled “Automatic Excavation Control System and Method”.
Other Means of Forming Underground Drilling Space
The mining and heavy civil underground industries have developed other processes that may be applied to forming drilling rooms for underground recovery of hydrocarbons. These include for example:    1. Hydraulic mining—Hydraulic mining techniques have been successfully demonstrated in the Alberta oil sands. Proposals have been put forward which involve mining the oil sand by hydraulic means through wells sunk from the surface. Such efforts are described, for example, in “Feasibility of Underground Mining of Oil Sand”, Harris and Sobkowicz, 1978 and “Feasibility Study for Underground Mining of Oil Sand”, Hardy, 1977. Johns in U.S. Pat. No. 4,076,311 issued Feb. 28, 1978 entitled “Hydraulic Mining from Tunnel by Reciprocated Pipes” discloses a method of hydraulic underground mining of oil sands and other friable mineral deposits. The present inventors have disclosed a method of hydraulic mining in oil sands in U.S. Patent Provisional Application 60/867,010 entitled “Recovery of Bitumen by Hydraulic Excavation” filed Nov. 22, 2006. The method of hydraulic mining disclosed includes: several means of drilling production and tailings injection wells; several means of augmenting hydraulic excavation for example by inducing block caving; means of isolating the underground personnel areas from formation gases and fluids; and means of backfilling the excavated volumes with tailings.    2. Horizontal secant pile—Secant pile walls or tunnels may be formed by constructing a longitudinal assembly of piles which contact each other to define a tunnel. The volume contained inside the pile assembly is excavated using the piles as ground support. The piles may be fabricated, for example, from steel tubes or reinforced concrete. The piles may be installed by pipe-jacking, pile driving, drilling or augering. Primary piles are installed first with secondary piles constructed in between primary piles once the latter gain sufficient strength. Pile overlap is typically in the order of about 50 to 100 mm.    3. Soil Mixing—Various methods of soil mixing (sometimes referred to as jet grouting), mechanical, hydraulic, with and without air, and combinations of both types have been used widely in Japan for about 20 years and more recently have gained wide acceptance in the United States. The soil mixing, ground modification technique, has been used for many diverse applications including building and bridge foundations, retaining structures, liquefaction mitigation, temporary support of excavation and water control. Names such as Jet Grouting, Soil Mixing, Cement Deep Mixing (CDM), Soil Mixed Wall (SMW), Geo-Jet, Deep Soil Mixing, (DSM), Hydra-Mech, Dry Jet Mixing (DJM), and Lime Columns are known to many. Each of these methods has the same basic root, finding the most efficient and economical method to mix cement (or in some cases fly ash or lime) with soil and cause the properties of the soil to become more like the properties of a soft rock.    4. Ground modification (also known as ground freezing)—Historically, ground modification for civil applications has been used primarily on large projects where groundwater and caving soils create an unstable situation and ground freezing represents the only possible solution. Ground freezing has been used to stabilize excavation walls in caving soils and to prevent groundwater seepage into the deep excavations near existing structures. The technology has been applied in Europe and North America for more than a century on a variety of construction and mining projects. The freezing method aims to provide artificially frozen soil that can be used temporarily as a support structure for tunneling or mining applications. It is a versatile technique that increases the strength of the ground and makes it impervious to water seepage. Excavation can proceed safely inside the frozen ground structure until construction of the final lining provides permanent support. In contrast to grouting works the freezing method is completely reversible and has no environmental impact. Ground freezing is not limited by adverse ground conditions and may be used in any soil formation, regardless of structure, grain size, permeability or moderate groundwater flow.    5. NATM—New Austrian Tunnelling Method (NATM) As defined by the Austrian Society of Engineers and Architects, the NATM “ . . . constitutes a method where the surrounding rock or soil formations of a tunnel are integrated into an overall ringlike support structure. Thus the supporting formations will themselves be part of this supporting structure.” In world-wide practice, however, when shotcrete is proposed for initial ground support of an open-face tunnel, it is often referred to as NATM. In current practice, for soft-ground tunnels which are referred to as NATM tunnels, initial ground support in the form of shotcrete (usually with lattice girders and some form of ground reinforcement) is installed as excavation proceeds, followed by installation of a final lining at a later date. Soft ground can be described as any type of ground requiring support as soon as possible after excavation in order to maintain stability of the NATM for soft ground. As long as the ground is properly supported, NATM construction methods are appropriate for soft-ground conditions. However, there are cases where soft-ground conditions do not favor an open face with a short length of uncompleted lining immediately next to it, such as in flowing ground or ground with short stand-up time (i.e., failure to develop a ground arch). Unless such unstable conditions can be modified by dewatering, spiling, grouting, or other methods of ground improvement, then NATM may be inappropriate. In these cases, close-face shield tunneling methods may be more appropriate for safe tunnel construction.
Key features of the NATM design philosophy are:                The strength of the ground around a tunnel is deliberately mobilised to the maximum extent possible.        Mobilisation of ground strength is achieved by allowing controlled deformation of the ground.        Initial primary support is installed having load-deformation characteristics appropriate to the ground conditions, and installation is timed with respect to ground deformations.        Instrumentation is installed to monitor deformations in the initial support system, as well as to form the basis of varying the initial support design and the sequence of excavation.        
Key features of NATM construction methods are:                The tunnel is sequentially excavated and supported, and the excavation sequences can be varied.        The initial ground support is provided by shotcrete in combination with fibre or welded-wire fabric reinforcement, steel arches (usually lattice girders), and sometimes ground reinforcement (e.g., soil nails, spiling).        The permanent support is usually (but not always) a cast-in-place concrete lining.        
It should be noted that many of the construction methods described above were in widespread use in the US and elsewhere in soft-ground applications before NATM was described in the literature.
For underground recovery of hydrocarbons, there remains a need for modified excavation methods and a selection method to utilize shafts as an underground base to install a network of wells either from the shaft itself or drilling rooms, tunnels and the like, initiated from the shaft. There is a need for safe and economical process of installing a network of hydrocarbon recovery wells from an underground work space while maintaining isolation between the work space and the ground formation. It is the objective of the present invention to provide a method and means of selecting the most appropriate process for providing adequate underground workspace by selecting one or more of a number of methods for installing, operating and servicing a large number of wells in various levels of a hydrocarbon deposit which may contain free gas, gas in solution and water zones.
For underground recovery of hydrocarbons, there remains a need for modified excavation methods and a selection method to utilize shafts as an underground base to install a network of wells either from the shaft itself or drilling rooms, tunnels and the like, initiated from the shaft. It is the objective of the present invention to provide a method and means of selecting the most appropriate process for providing adequate underground workspace by selecting one or more of a number of methods for installing, operating and servicing a large member of wells in various levels of a hydrocarbon deposit which may contain free gas, gas in solution and water zones.